1a.Objectives (from AD-416)
The long term objective is to increase sorghum grain utilization by identifying the physical and biochemical components important for food, feed, and bio-industrial quality. Over the next 5 years, the following specific objectives will be addressed: Objective 1: Identify optimum kernel characteristics for processing of sorghum. Objective 2: Determine role of starch, proteins, phenolic compounds and their interactions in digestibility and functional quality of sorghum. • Sub-objective 2.A. Determine the molecular basis for protein cross-linking in sorghum and its impact on functionality and digestibility of sorghum. • Sub-objective 2.B. Determine the relationships between starch content, composition and granule size on functionality and digestibility of sorghum. • Sub-objective 2.C. Ascertain the interactions between and among sorghum phenolic compounds, protein and starch. • Sub-objective 2.D. Determine how physical and biochemical properties of the kernel influence mold resistance and are related to processing quality. Objective 3: Determine the impact of the environment on sorghum kernel structure and composition as well as their relationship to end use quality. Objective 4: Develop biochemical and physical markers to predict end-use quality of sorghum grain for food and feed uses.

1b.Approach (from AD-416)
Objective 1 addresses the relationships among physical grain structure, roller milling, and flour quality for the manufacture of wheat-free sorghum food products. Objectives 2a and 2b further investigate sorghum flour quality by addressing the functional and nutritional role of protein and starch in end-use quality of sorghum. Objective 2c is intertwined with Objectives 1, 2a, and 2b by studying the interaction among phenolic acids, proteins and starch. Objective 2d combines key factors from Objectives 1, 2a, 2b, and 2c through the impact of grain hardness, proteins, and phenolic compounds on mold resistance. Not only do these components play a role in mold resistance, but damage to sorghum grain by mold alters hardness (thus milling and flour quality, Objective 1), biochemical properties of sorghum (thus functionality, Objective 2a, b, and c). Objective 3 aims to better understand the process of grain development in sorghum which provides supporting information for the primary Objectives 1 and 2. Objective 4 is also a supportive objective geared towards providing “tools” to assist in achieving Objectives 1-3. This project addresses processing of sorghum into flour, describes how the biochemical components of the flour affect the functional and nutritional quality of the flour and how mold resistance also influences grain and flour quality.

3.Progress Report
This project (5430-44000-023-00D) falls under National Program 306, component 1 which focuses on “maintaining the quality” and “enhancing their marketability” as well as “expanding domestic and global market opportunities.” Progress was made on all objectives of the project. Several new methods were developed for screening sorghum for important end-use properties including protein digestibility (important for food, fuel and feed), phenolic acid content (important for anti-oxidant properties), starch damage (important for sorghum flour quality) and mold levels (important for all end-uses).

Substantial progress was made screening a diverse set of sorghum samples for important end-use quality traits. Physical grain traits such as grain weight, diameter and hardness were measured on a large (n=~300) genetically diverse collection of samples. Starch was purified from these same samples and a number of traits, such as starch granule size distribution, were measured. A large number of samples from this sample set were also screened for anti-oxidant levels. Screening this genetically diverse sample set for various end-use quality traits will enable the sorghum breeding and genetics communities to identify germplasm sources for use in developing sorghum lines with improved quality traits.

4.Accomplishments
1.
Rapid method to predict digestibility in sorghum. Sorghum is known to have lower protein digestibility than other cereal grains. One avenue to improve this is to identify sorghum lines with inherently high levels of protein digestibility. ARS researchers at Manhattan, Kansas, developed a rapid method to predict protein digestibility in sorghum. This will allow screening of diverse sorghum populations and identify potential sources of high protein digestibility for the sorghum breeding community.

2.
Rapid method to measure starch damage in sorghum. During milling of grains, starch granules are physically damaged. This damage directly impacts the quality of flour. High levels of starch damage, specifically in sorghum flour, have been shown to be detrimental to sorghum bread quality. Current methods for measuring starch damage in flours are slow and labor intensive. ARS researchers in Manhattan, Kansas, demonstrated that a commercial instrument designed to rapidly measure starch damage in wheat could be successfully applied to sorghum. This will aid the sorghum industry in determining sorghum lines that have improved flour quality and in evaluating the effect of milling on sorghum flour quality.